Please refer to FIG. 1. FIG. 1 shows a schematic block diagram of a conventional storage system 100 having a universal serial bus (USB) protocol. The storage system 100 includes a disk driver 102, a storage class driver 104 and USB driver 106. The storage system 100 is coupled to the USB storage 108. When the storage system 100 accesses the USB storage 108, the disk driver 102 transmits an input/output request packet (IRP) to the storage class driver 104 so that the USB driver 106 generates a USB request block (URB) message to access the data stored in the USB storage 108 via the URB message. Each of the IRPs corresponds to a URB message and an address, e.g. one of address “A_1” through “A_n”. In addition, there is data I/O between the USB driver 106 and the USB storage 108. However, the disadvantage of the storage system 100 is that each of the IRPs generates a URB message, i.e. one of URB messages “URB_1” through “URB_n”. Further, each URB message is transmitted to the USB driver 106 based on the format of command (“C_1” through “C_n”), data and status (“S_1” through “S_n”). When the data transmission is increased between the disk driver 102 and the USB storage 108, it takes a lot of transmission time to transfer the commands and statuses. Specifically, when the data with smaller address length are transmitted, it wastes a lot of transmission time. Consequently, there is a need to improve the transmission rate of the storage system.